The first thing I notice (other than the fact that it's a paragraph, not a sentence?) is the alternate possible meanings for the second word in the first sentence. The use of had here allows for different possible meanings. The first is probably most easily understood as "We'd", meaning that whoever we is actually did the publishing. The second may be understood as synonymous with the phrase "We'd arranged to have published...", meaning that is was someone else who did the publishing. So if your version of "correct" is that it affords as little ambiguity as possible, I suspect you'd class that aspect of the first sentence as incorrect. It appears a more preferable initial sentence would be
We published our OpenCCU source code at the beginning of 2002.
The second sentence also flirts with the word had in what may be perceived as a similarly problematic way. But it's the use of the word on there instead of the word onto which allows for an even larger amount of ambiguity, (though it's easy to proclaim that ambiguity irrelevant depending on any number of possible contextual factors). If Sourceforge was the destination, as it no doubt was, the word onto makes that incontrovertibly clear, while the word on allows Sourceforge to be the place from which the uploading took place.
From there, if you don't mind the critique, the largest problem centers around the way that the second sentence begins, that is, the use of the term "At first". This of course is synonymous with the adverb initially, modifying the verb "we had uploaded". The reason this is problematic is that by sheer dint of use (inclusion) it implies a contrast between that moment and another moment at some point in the future, near or far. It implies an "And then later...". Unfortunately, the next adverb immediately fails quite understandably to accomplish that contrast. It appears that what the second sentence intends to communicate is something more along the lines of
And the instant we uploaded our source code onto Sourceforge we began receiving thanks as well as wishlist items for the future OpenCCU development.
Finally, the phrase "for the future OpenCCU development" is also perhaps less effective than it could be, though certainly most readers would understand that it apprehends work that may be done on items from the aforementioned wishlist. Largely it is the use there of the preposition for which accounts for the drag, because for can also mean on behalf of or on trade, etc. Cleaning that up seems appropriate. And frankly, the very concept of a wishlist implies not only the future but, indeed, the need for development. And the fact that OpenCCU would accomplish that development is also sufficiently provided for by context alone. So it can be excluded outright.
In sum then, the following construction appears more suitable
We published our OpenCCU source code at the beginning of 2002, and the instant we uploaded it onto Sourceforge we began receiving thanks as well as wishlist items.